Veneer lathe log charger system having enhanced accuracy and rate of production

ABSTRACT

A veneer lathe charger system utilizing automated equipment for scanning and positioning a log to obtain optimum production of veneer therefrom. The charger has mechanical features specially designed to provide a degree of accuracy in the physical manipulation of the log comparable to the degree of accuracy provided by the automated scanning and positioning equipment. These include log manipulation features emphasizing engagement of the log only at its opposing ends during and after scanning and especially during transfer from one manipulating device to another, avoidance of end engagement by two different manipulating devices in identical end areas of the log, minimal movement of log positioning devices by the employment of dual scanning steps and features for retaining the accuracy of the manipulation devices despite wear thereof. The charger further includes features for improving its rate of production by reducing time delays between successive log manipulating steps.

BACKGROUND OF THE INVENTION

This invention relates to improvements in log charger systems for veneerlathes. More particularly the invention relates to improvements in suchcharger systems having automated scanning equipment for sensing theshape of a log and positioning the log for optimum production of veneer.

In the design of veneer production equipment, the primary objectives areto maximize the yield of usable veneer from the irregularly-shaped logsfrom which the veneer is peeled, and to maximize the production rate ofthe veneer. In order to attain these objectives great effort has beenexpended in the development of sophisticated, automated log scanningequipment, primarily of the electro-optical type, for sensing the shapeof each log and rapidly determining its longitudinal axis for optimumveneer production. Examples of such scanning systems used or usable forthis purpose are contained in the following U.S. Pat. Nos. 3,736,968;3,746,065; 3,787,700; 3,852,579; 3,890,509; 3,902,539; 3,992,615;4,197,888; and 4,221,973. Electro-optical scanners constructed inaccordance with the foregoing technology, and particularly those whichrotate the log during the scanning process, are extremely accurate andhave the capability of determining the location of the log axis foroptimum veneer production to within a few thousandths of an inch.

While such a high degree of accuracy in determining the optimum peelingaxis should theoretically maximize the yield of veneer from each log,the results obtainable in practice have unfortunately fallen short ofthis goal because the mechanical log manipulators of veneer lathechargers are incapable of duplicating the scanner's degree of accuracy.Thus, although the scanning system may identify the location of theoptimum peeling axis of a log to within a few thousandths of an inch,the mechanical log manipulators responsible for aligning such axis withthe rotational axis of the lathe actually allow a much wider margin forerror than that tolerated by the scanning system. Because of thisdiscrepancy in tolerances between the electro-optical and mechanicalportions of veneer lathe chargers, substantial mispositioning of thelogs and less than optimum yields persist despite the provision of thehighly accurate scanning systems.

The progress of log manipulating mechanisms, as opposed to scanningsystems, in veneer lathe chargers is exemplified by U.S. Pat. Nos.3,037,538, 3,664,395, 3,746,065, 3,752,201, 4,197,888 and 4,246,940. Ingeneral, all of such chargers attempt to hold the log at either aprepositioning or a scanning station to determine its optimum peelingaxis, adjust the position of the log such that the optimum axis isaligned with a reference axis, and transfer the log to the veneer lathesuch that the optimum axis is aligned with the rotational axis of thelathe. In these few mechanical steps, however, there are manyopportunities for log positioning errors. Relatively large errors canoccur, for example, if at any point from the initiation ofprepositioning or scanning to the securing of the log in the lathe, thelog is supported by engagement with its curved surface at pointsintermediate its ends, rather than by end engagement. The error problemis further compounded when rotary scanning is not used and the optimumaxis is therefore determined from insufficient information regarding thelog's profile.

In addition to mechanical inaccuracy, the speed of log manipulation byveneer lathe chargers has been hampered by unnecessary time lags betweenlog manipulating steps, thereby adversely affecting production rate.

SUMMARY OF THE PRESENT INVENTION

The present invention is directed to an improved veneer lathe chargersystem which increases the rate of production of the charger and itsassociated veneer lathe. The rate of production of the charger andveneer lathe are improved by minimizing the waiting time between therotary scanning step and the transfer of the log from the rotary scannerto the log transfer device. Conventionally the rotary scanner waitsuntil the log finishes its rotational movement before finally adjustingthe log's position to align its optimum peeling axis. However, in thepresent invention, such adjusting is begun immediately after the log hascompleted one revolution and takes place before it has finished itsrotational movement so that, as soon as the log's rotational movementhas stopped, it can immediately be engaged by the log transfer device.

Accordingly it is a principal objective of the present invention toimprove the production rate of a veneer lathe charger and its associatedlathe.

The foregoing and other objectives, features and advantages of thepresent invention will be more readily understood upon consideration ofthe following detailed description of the invention taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified perspective view of the major elements of thepreferred veneer lathe charger and its associated lathe in accordancewith the principles of the present invention.

FIG. 2 is a more detailed side view of the apparatus of FIG. 1.

FIG. 3 is an enlarged end view of an exemplary log showing therelationship between the end-engaging element of a rotary log scannerspindle of the present invention and that of its associated loadingdevice.

FIG. 4 is an enlarged end view of an exemplary log showing therelationship between the end-engaging element of a rotary log scannerspindle of the present invention and that of its associated log transferdevice.

FIG. 5 is an enlarged, sectional side view of a rotary scanner spindleof the present invention.

FIG. 6 is an enlarged cross-sectional view taken along line 6--6 of FIG.5.

FIG. 7 is an enlarged, partially sectional view of a simplified rotaryscanner suitable for use in the present invention.

FIG. 8 is a perspective view of the log transfer device employed in thepresent invention.

FIG. 9 is a schematic diagram of an exemplary fluid ram assembly and itsassociated position sensor, servo valve and controller of the typeutilized with each of the various log manipulators of the presentinvention.

FIGS. 10 and 11 are enlarged sectional views of respectiveposition-sensing devices for the various log manipulators of the presentinvention.

FIG. 12 is an exploded perspective view of a respective scanner loadingdevice of the present invention.

FIG. 13 is a partially schematic, partially sectional view of typicalfluid pressure-biased bearing surfaces employed in the presentinvention, shown particularly with respect to the scanner loading deviceof FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENT GENERAL ARRANGEMENT

FIG. 1 depicts schematically, and FIG. 2 shows in greater detail, thepreferred general arrangement of the veneer lathe charger, indicatedgenerally as 10, with respect to the veneer lathe, indicated generallyas 12. Successive logs 14 approach the charger 10 on a conveyer 16, fromwhich they are deposited onto an upwardly sloped conveyer 18 havingsuccessive sets of spaced lugs 20 which position the logs atpredetermined intervals along the conveyer 18. Arms 22 position each log14 longitudinally on the conveyer 18 and sense its length. As the logs14 proceed up the conveyer 18, they pass through a preliminary scanner24, to be described in greater detail hereafter, which roughly sensesthe shape of each log and thereby determines the location of apreliminary optimum peeling axis of the log. The log 14 proceeds pastthe scanner 24 to a station indicated by the position of log 14a wherethe conveyer stops momentarily. A pair of log-engaging devices 26 engagethe opposing ends of the log at this point and raise the log upwardly toa position, indicated by log 14b, wherein the preliminary optimumpeeling axis of the log, as determined by the preliminary scanner 24, isaligned with the rotational axis 27 of a pair of rotary spindles 28which engage the opposing ends of the log. The primary spindles 28rotate the log through a complete revolution while a rotary finalscanner 30 senses the log's shape so as to determine the preciselocation of the optimum peeling axis of the log. The rotary spindles 28are then adjusted horizontally and vertically so as to align the optimumpeeling axis, as determined by the final scanner 30, with apredetermined reference axis. While such adjusting is taking place, thespindles 28 further rotate the log to a position where it can be engagedby a pair of end-engaging transfer arms 32 which then transfer the logfrom the spindles 28 to the spindles 34 of the veneer lathe 12 such thatthe optimum peeling axis of the log is aligned with the rotational axisof the lathe 12. The veneer lathe 12 includes a peeling knife 36 mountedon a carriage 38 which is reciprocated toward and away from therotational axis of the veneer lathe by ball screws such as 40. Peelingof the log occurs as the knife 36 is advanced toward the rotational axisof the lathe and, when the log has been reduced by peeling to apredetermined diameter, the knife 36 is retracted and the remnant of thelog is released from the lathe spindles 34 and ejected tranversely by aconveyer 42 (FIG. 2).

PRELIMINARY SCANNING

Preliminary scanning of a log 14 takes place as it travels up conveyer18 past scanner 24. Scanner 24 is a computerized electro-optical scannerof any suitable known type, such as those shown in U.S. Pat. Nos.3,736,968, 3,746,065 or 3,890,509, the disclosures of which areincorporated herein by reference. Preliminary scanner 24 determines theprofile dimensions of the log 14 with respect to two planes intersectingthe ends of the log, and is thereby able to compute a preliminaryoptimum peeling axis of the log in a manner already well-known to theart. It should be noted that, although electro-optical scanningtechniques are preferred for use in the present invention, other typesof scanners which likewise are capable of sensing the shape of a log,such as sonic or air scanners, are not foreclosed.

In FIG. 2, the location of one end of the preliminary optimum peelingaxis C_(p) (as determined by the preliminary scanner 24) of a relativelysmall diameter log 14 is shown. The different location of the end of thepreliminary optimum peeling axis C_(p) ' of a much larger diameter log14' is also shown for purposes of comparison. Although the two axesC_(p) and C_(p) ' are at different elevations relative to the slopedconveyer 18, it will be noted that they are substantially alignedvertically. This is because conveyer 18 is constructed such that itsacute forward angle of slope is the same as the acute rearward angle ofslope of the log-engaging faces of the lugs 20. Thus the locations ofthe preliminary optimum peeling axes of different diameter logssupported by the V-shaped supporting surfaces formed by the lugs 20 andconveyer 18 do not vary horizontally with respect to the junction point44 between the conveyer and the lugs merely because of diameterdifferences. Rather horizontal variations in optimum axis location willoccur only due to log profile irregularities, and therefore suchvariations will be of lesser magnitude that if they were affected bydiffering diameters.

When the log arrives at position 14a adjacent the log-engaging devices26, the conveyer stops momentarily with the junction point 44 in apredetermined relation to the devices 26. Each log-engaging device 26 ismounted on a vertically oriented slide 48 (FIG. 12) slidably mounted tothe frame 50 of the charger 10. The slide 48 permits each log-engagingdevice 26 to be moved vertically along a rectilinear path which bisectsthe included angle θ between the conveyer 18 and the log-engagingsurfaces of the lugs 20. Each log-engaging device 26 is also extensibleand retractable toward or away from the end of the log by virtue of ahorizontal slide 52 which is mounted in the head of the slide 48.Vertical motion of the log-engaging device 26 is controlled by adouble-acting hydraulic ram assambly 54 in response to a servo valve andcontroller (not shown) receiving continuous vertical position-sensingfeedback information from a position sensor 56 in a manner to bedescribed more fully hereafter. Horizontal extension and retraction ofthe log-engaging device 26 is likewise controlled by a double-actinghydraulic ram assembly 58 in response to a valve and controller (notshown) receiving horizontal position feedback information from aposition sensor 60.

As each respective log approaches position 14a the controller of ramassemblies 54, in response to the height of the preliminary optimumpeeling axis determined by the preliminary scanner 24, verticallyadjusts the height of each respective log-engaging device 26individually such that the top of the respective log-engaging device 26will be a fixed predetermined distance below the location of thepreliminary optimum axis on the respective end of the log when the logstops at position 14a. Such vertical adjustment in most cases results inthe two log-engaging devices 26 being at different elevations, since thenatural tapered diameter of the log causes the location of thepreliminary optimum axis to be higher at one end than the other. Whenthe conveyer 18 stops the log at the position 14a, the log-engagingdevices 26 are extended by their respective ram assemblies 58 intopositive clamping engagement with the opposing ends of the log.

Because each log-engaging device 26 has been adjusted into predeterminedelevational relation with the preliminary optimum peeling axis of thelog, the elevational relationship between the preliminary optimum axisand each log-engaging device 26 is fixed. Accordingly, the log-engagingdevices 26 raise the log from the position 14a vertically upward untilthe devices 26 assume the same elevational relationship, with respect tothe rotational axis 27 of the rotary spindles 28, that they previouslyassumed with respect to the preliminary optimum axis of the log prior toengaging it. This assures that the preliminary optimum axis of the log,as determined by the preliminary scanner 24, is horizontally alignedwith the rotational axis 27 of the rotary scanner spindles 28.

Likewise, the horizontal relationship between the end-engaging devices26 and the preliminary optimum axis is fixed by the place where theconveyer 18 stopped the log at the position 14a relative to the devices26. Accordingly, if the conveyer stopped the log such that thepreliminary optimum axis was aligned vertically with the center of eachdevice 26, then the respective rotary scanner spindle 28 is adjustedhorizontally, in a manner to be described hereafter, so that itsrotational axis is likewise vertically aligned with the center of therespective log-engaging device 28. Alternatively, if the conveyerstopped the log such that the preliminary optimum axis was offsethorizontally from the center of the respective log-engaging device 26,then the respective spindle 28 is likewise adjusted horizontally so thatits rotational axis 27 assumes the same offset.

The end result of these procedures is that, by virtue of the cooperationbetween the log-engaging devices 26 and the rotary scanner spindles 28,the log is moved by the devices 26 into a position whereby itspreliminary optimum peeling axis, as determined by the scanner 24, isaligned with the rotational axis 27 of the spindles 28. Because there isno horizontal variation in the optimum peeling axis location relative tothe conveyer 18 merely due to log diameter differences, as explainedabove, and because vertical variations in the optimum peeling axislocation are accounted for by vertical adjustment of the log-engagingdevices 26, the magnitude of adjustment of the spindles 28 necessary toachieve such alignment is small. This is important because the primaryobjective of the preliminary scanning step is to obviate the need forany large-magnitude adjusting movement of the spindles 28, therebyenabling their adjusting mechanisms to be designed exclusively forextremely fine, accurate adjustment pursuant to final scanning of thelog as described hereafter.

FINAL SCANNING

When the log has been raised to the above-described position ofalignment with the rotary scanner spindles 28, such position beingdesignated as 14b, the relationship of each end of the log to therespective log-engaging device 26 and associated rotary scanner spindle28 is as shown in FIG. 3. The preliminary optimum pelling axis C_(p) asdetermined by scanner 24 is aligned with the rotational axis 27 of therespective spindle 28. The respective log-engaging device 26, whosefunction it is to load the log into the rotary scanner spindle 28, isengaging the end of the log a predetermined distance "D" below thepreliminary optimum axis C_(p). The log-engaging portion of the rotaryspindle 28 is asymmetrically offset from its rotational axis 27 and thespindle 28 is rotatably positioned so that such log-engaging portion isabove the rotational axis 27. In this position, as shown in FIG. 3, eachrotary spindle 28 is extended into end engagement with the log while thelog remains engaged by the respective log-engaging devices 26. Suchsimultaneous end engagement of the log by both devices between which thelog is being transferred is significant in maintaining the preliminaryoptimum axis C_(p) in a known position, and is made possible by the factthat both log-engaging devices 26 and 28 are designed to engage the endof a log only within separate portions or sectors of a circular areasurrounding the rotational axis 27 of the respective spindle 28.

It is further significant that the two separate end portions of the logengaged by the respective devices 26 and 28 are both spaced radiallyfrom the rotational axis 27 of the spindle 28 so as to thereby leave acircular area 62 surrounding the rotational axis 27 free of engagementby either device. This circular area is reserved for ultimate engagementof the log by the veneer lathe spindles 34. Reservation of this circulararea is important because each of the log-engaging devices 26 and 28 hasa series of penetrating spikes 64, 66 which create cavities in the endof the log. These cavities, if present in the end area where the lathespindles 34 will subsequently engage the log, could cause misguidance ordeflection of the log as the spindles engage its ends, therebydeflecting the optimum peeling axis out of its desired alignment withthe rotational axis of the lathe 12. If the lathe is equipped withconcentric outer and inner spindles, as is common, it is necessary onlythat the circular area 62 be large enough to contain the inner orsmaller spindle since the inner spindle is the first to engage the login the lathe and thus controls its alignment.

FIG. 5 is a sectional side view of one of the rotary scanner spindles 28together with its associated rotating, extending and retracting, andhorizontal and vertical position adjustment mechanisms respectively. Thespindle 28 is shown in FIG. 5 in the same rotational orientation, and inthe same spatial relationship with respect to its associatedlog-engaging device 26, as is depicted in FIG. 3. Extension of thespindle 28 into engagement with the end of the log while the end issimultaneously engaged by log-engaging device 26 is accomplished byretraction of a double-acting fluid ram assembly 68 which pulls ahousing 70 horizontally toward the end of the log. The housing 70, whichis rectangular in cross section as best seen in FIG. 6, is slidablymounted for horizontal movement within a rectangular sleeve 72, and hasa rotary hydraulic motor 74 mounted therein driving a shaft 76 whichselectively rotates the spindle 28. Elongate bearing pads 78 (FIGS. 5and 6), mounted within the sleeve 72 and biased by a predetermined fluidpressure against the housing 70, provide frictional sliding engagementbetween the housing 70 and the sleeve 72. Horizontal extension andretraction of the housing 70 with respect to the sleeve 72 is controlledby the hydraulic ram assembly 68 in response to a valve and controller(not shown) receiving horizontal position feedback information from aposition sensor 80.

After the spikes 66 of the rotary scanner spindle 28 have penetrated theend of the log pursuant to the extension of the housing 70 toward theend of the log, the respective log-engaging device 26 is withdrawn fromthe end of the log by the retraction of ram assembly 58 (FIG. 12).Thereafter each respective hydraulic motor 74 rotates its respectivespindle 28, and thereby the log, through a full 360° revolution whilethe profile of the log is sensed, preferably at 15° increments, by thefinal scanner 30. Scanner 30 is a computerized electro-optical rotaryscanner of any suitable known type, such as those shown in U.S. Pat.Nos. 3,852,579, 3,992,615 or 4,221,973, the disclosures of which areincorporated herein by reference. Preferably, an electro-optical systemof the type shown in U.S. Pat. No. 4,221,973 is used in combination witha data processing system of the type shown in U.S. Pat. No. 3,852,579 todetermine the final optimum peeling axis of the log.

After one full revolution of the log, the scanner 30 has obtained a fullview of the shape thereof and has computed the final optimum peelingaxis which, because of the more precise nature of the final scanner 30compared to the preliminary scanner 24, will usually have a somewhatdifferent position than the preliminary optimum peeling axis. Pursuantto the determination of the final optimum peeling axis of the log by thefinal scanner 30, the positions of the respective spindles 28 are thenadjusted horizontally and vertically so as to align the final optimumpeeling axis with an imaginary reference axis parallel to the rotationalaxis of the veneer lathe 12. The imaginary reference axis has the samespatial relationship with respect to the log-engaging ends of thetransfer arms 32, when such arms are in position to receive the log fromthe spindles 28, as the veneer lathe's rotational axis has with respectto the arms 32 when the arms are in position to permit engagement of thelog by the lathe spindles 34. Accordingly, due to adjustment of thescanner spindles 28 the final optimum peeling axis of the log, after thelog is transferred by the arms 32 to the lathe spindles 34, will bealigned with the rotational axis of the lathe spindles.

Horizontal and vertical fine adjustment of the spindles 28 to align thefinal optimum peeling axis with the aforementioned reference axis isaccomplished by means of a mechanism shown in FIG. 2 and in greaterdetail in FIGS. 5 and 6. Each sleeve 72 is mounted for horizontal andvertical adjustment within a rectangular frame 82. The sleeve 72 isslidable horizontally with respect to the frame 82 by means of a pair ofslides 84 frictionally engaging elongate bearing pads 86. Horizontalmovement of the sleeve 72 within the frame 82 is controlled by a pair ofsingle-acting opposed hydraulic ram assemblies 88 in response to a servovalve and controller (not shown) receiving horizontal position feedbackinformation from a horizontal position sensor 90. Vertical adjustment ispermitted by vertical movement of the entire frame 82 with respect tothe frame 50 of the charger, in which the frame 82 is slidably mountedfor vertical movement by a pair of slides 92. Such vertical movement iscontrolled by a double-acting hydraulic ram assembly 94 in response to aservo valve and controller (not shown) receiving vertical positionfeedback information from a position sensor 96.

Although final scanning of the log is completed after one completerevolution thereof, i.e with the spindle 28 once again in the rotaryorientation shown in FIG. 3, rotation of the log by the spindles 28 isnot complete at this point. Rather the spindles 28 continue to rotatethe log a further fraction of a revolution until the spindle 28 of FIG.3 assumes the rotary orientation shown in FIG. 4. During this fractionof a revolution, the above-described horizontal and vertical adjustmentof the spindles 28 takes place such that, when the spindles 28 reach therotary orientation shown in FIG. 4, the final optimum peeling axis ofthe log as determined by the final scanner 30 is aligned with theaforementioned imaginary reference axis. Such adjustment of the spindles28 while the log is still being rotated eliminates an otherwiserepetitive period of delay between final scanning and the transfer ofthe log to the lathe 12, thereby enhancing the overall production rate.

TRANSFER OF THE LOG TO THE LATHE

When the spindles 28 have rotated the log to the position depicted inFIG. 4 and have been horizontally and vertically adjusted so that thefinal optimum peeling axis of the log, exemplified by the designationC_(f) in FIG. 4, is aligned with the above-identified reference axis R,the transfer arms 32 are positioned adjacent the ends of the log in apredetermined fixed spatial relation to the reference axis R. At thispoint the respective spindle 28 and transfer arm 32 have a relationshipto one another generally as shown in FIG. 4, although it will beunderstood that the position of the spindle 28 relative to the transferarm 32 will vary from log to log depending on the position of the finaloptimum peeling axis C_(f) relative to the preliminary optimum peelingaxis C_(p). This is because the transfer arm 32 has a fixed,predetermined relationship only with respect to the reference axis (andthus the final optimum peeling axis C_(f) which has been aligned withthe reference axis), and not with respect to the preliminary axis C_(p)or rotational axis 27 of the spindle 28. However, because ofprescanning, the rotational axis 27 of the spindle 28 and thepreliminary axis C_(p) should not be far removed from the final optimumpeeling axis C_(f) and reference axis R.

Accordingly, in the position of FIG. 4, each transfer arm 32 is clampedinto end engagement with the log while the log remains engaged by therespective rotary spindles 28. Such simultaneous end engagement of thelog by both devices between which the log is being transferred has thesame significance as previously discussed with respect to the transferfrom the log-engaging device 26 to the rotary spindle 28, i.e. itmaintains the log in a known position with respect to both devices. Suchsimultaneous end engagement is made possible by the fact that the rotaryspindles 28 and transfer arms 32 respectively engage the end of a logonly within separate portions or sectors of a circular area surroundingthe rotational axis 27 of the respective spindle 28. It is furthersignificant that the two separate end portions of the log engaged by therespective devices 28 and 32 are both spaced radially from therotational axis 27 of the spindle 28 so as to thereby leave theaforementioned circular area 62 surrounding the rotational axis 27 freeof engagement by either device. Thus this circular area remains reservedfor ultimate engagement of the log by the veneer lathe spindles 34 aspreviously discussed.

It will also be noted that the transfer arms 32 engage the end of thelog in approximately the same area where the log-engaging device 26(FIG. 3) previously engaged the log, i.e. in a location generallydiametrically opposed to the log-engaging portion of the spindle 28. Toavoid any misguidance or deflection of the log with respect to thetransfer arms 32 as they engage the log due to the cavities left by thepenetrating spikes 64 of the log-engaging device 26, the penetratingspikes 98 of the transfer arms 32 are arranged in a patternsubstantially different from the pattern of spikes 64 so that thepenetrations of spikes 98 will generally occur at different locations onthe end of the log than the penetrations of spikes 64, even though bothspike patterns generally cover the same end area of the log.

FIG. 8 shows the actuating mechanism for the transfer arms 32. Thetransfer arms are reciprocated transversely into and out of endengagement with the log by virtue of the fact that each arm 32 has arespective carriage 100 at its upper end both pivotal and transverselyslidable with respect to a pair of transverse rods 102. Transversesliding of the carriages 100 toward or away from one anotheralternatively to engage or release the ends of a log is controlled by apair of double-acting hydraulic ram assemblies 104 in response to valvesand controllers (not shown) receiving transverse position sensingfeedback information from respective position sensors 106. With thetransfer arms 32 positioned as shown in FIG. 4, ram assemblies 104 aresimultaneously retracted pulling the carriages 100 and thus the arms 32toward one another into end-engaging relationship with the log. Afterthe penetrating spikes 98 of the transfer arms 32 have penetrated theopposing ends of the log, the rotary scanner spindles 28 are eachretracted by extension of ram assembly 68 and the resultant retractionof housing 70 out of engagement with the log, thereby leaving the logsolely within the grasp of the transfer arms 32.

FIGS. 2 and 8 show the mechanism by which the transfer arms 32reciprocate in unison between the rotary scanner spindles 28 and thelathe spindles 34, so as to transfer the log to the lathe. The entiretransfer arm mechanism 32 is supported by the charger frame 50. Theupper end of each arm 32 (i.e. the upper end of each arm's carriage 100)is pivotally and transversely slidably connected to the upper rod 102 bybushings 108. The upper rod 102, rather than being affixed immovably tothe frame 50, is vertically movable with respect to the frame 50 byvirtue of its connection to the ends of a pair of idler arms 110 whichare pivotable vertically with respect to the frame 50. The verticalsupport for the arms 32 is thus not provided by the idler arms 110, butrather by the supportive interaction between a pair of tracks 112 on theframe 50 and a pair of rollers 114 rotatably connected to the ends ofthe lower rod 102.

The arms reciprocate between the rotary scanner and the lathe in unisonunder the control of a pair of double-acting hydraulic ram assemblies116 in response to servo valves and controllers (not shown) receivingposition sensing feedback information from a pair of position sensors118. Each position sensor 118 is connected by a respective crank arm 120to an end of the lower rod 102 so that the connections between theposition sensors 118 and the crank arms 120 correspond geometrically tothe connections between the ram assemblies 116 and the lower rod 102.Because of the provision of the supporting tracks 112 and the verticallymovable pivotal connection between the arms 32 and the upper rod 102, itwill be recognized that the upper ends of the arms 32 not only pivot butalso move vertically while the arms reciprocate between the finalscanner spindles 28 and the lathe 12. This arrangement has the advantageof both elevating and straightening the path of a log as it istransferred from the final scanner to the lathe without a requirementfor raising the position of the upper pivot point (about the upper rod102) to as high an elevation as would be required if the upper pivotpoint were fixed. This makes the transfer arm structure substantiallymore compact than it would otherwise be if it utilized a pure pivotinggeometry, allowing installation in structures having lower overheadclearance, while permitting sufficient clearance beneath the transferpath of a log to permit the advantageous utilization of a transverse logejection conveyer 32 without interference with a log being transferredby the conveyer 42. While the tracks 112 are rectilinear for sake ofsimplicity and economy, it would be possible to design such tracks witha curved or otherwise irregular shape so as to further straighten andelevate the path of transfer of a log from the final scanner to thelathe if such result were desired. Alternatively, controlled verticalmovement of the upper ends of the arms 32 to straighten and elevate thepath of transfer of the log could be achieved without any tracks 112 atall by providing fluid ram assemblies and associated position sensorsinteracting between arms 110 and the frame 50 to control the verticalpivoting movement of arms 110 and thus the vertical movement of theupper ends of the arms 32. In such case, arms 110 would provide thevertical support for the arms 32.

After the arms 32 have grasped the opposing ends of a log and such endshave thereafter been released by the rotary scanner spindles 28, ramassemblies 116 begin extending so as to transfer the log toward thelathe 12. When the arms 32 have brought the log to within apredetermined distance of the rotational axis of the lathe, where thereis not yet any danger of the log interfering with a preceding log beingpeeled by the lathe 12, the controllers of the servo valves whichoperate the ram assemblies 116 begin to receive input informationregarding the position of the peeling knife 36 of the lathe 12 as itpeels the preceding log. Such knife position is sensed by a positionsensor 122 (FIG. 1), of either the rotary encoder type as shown or ofthe linear type, connected to the ball screw 40 which controls thereciprocating movement of the knife blade 36 toward and away from therotational axis of the lathe. The continued movement of the arms 32 andtheir engaged log toward the rotational axis of the lathe 12 isthereafter responsive and proportional to the simultaneous movement ofthe knife blade 36 toward the rotational axis of the log, therebyenabling the log grasped by the arms 32 to move gradually closer to thelathe as the diameter of the preceding log becomes smaller as a resultof peeling. When peeling of the preceding log is finally completed, thelog held by the transfer arms 32 has already moved into very closeproximity with the rotational axis of the lathe 12. At this point thelathe spindles 34 are retracted, dropping the remnant of the precedingpeeled log onto the conveyer 42. However the log held by the transferarms 32 cannot yet be positioned for peeling because the peeling knife36 must be retracted. Rather than waiting for such retraction beforebeginning to move the log into proper peeling position, however, thecontrollers of the servo valves of the ram assemblies 116 cause furthergradual movement of the log toward the lathe in response and proportionto the retracting motion of the knife 36, as also sensed through theposition sensor 122. Accordingly, by the time the peeling knife 36 hasbeen fully retracted, the transfer arms 32 have brought the log intoproper peeling position with its final optimum peeling axis aligned withthe rotational axis of the lathe spindles 34. The spindles 34 thenengage the log, the transfer arms 32 release it, and the peeling knife36 is advanced in the conventional manner toward the rotational axis ofthe spindles 34 as the log is rotated by the spindles 34. Meanwhile thetransfer arms 32 are retracted, by the retraction of the ram assemblies116, back toward the rotary scanner spindles 28 so as to engage the nextlog in the manner previously described.

CALIBRATION

A continued high degree of accuracy of the charger 10 in itsmanipulation and alignment of logs is ensured by the ability of thesystem for self-calibration of the rotary scanner 30 and its relatedadjusting mechanisms. This is accomplished by peeling a log, which hasbeen scanned and properly aligned in the lathe in accordance with theabove-described procedures, to a known diameter and then, rather thanejecting the remnant of the peeled log, manually or automaticallycontrolling the operation of the transfer arms 32 to recover the remnantfrom the lathe spindles 34 and return the remnant to the rotary scannerspindles 28 for redetermination by the scanner 30 of the remnant'soptimum peeling axis. Accurate calibration and functioning of thecharger is indicated by the lack of need for any readjustment in theposition of the peeled remnant to realign its optimum peeling axis, asdetermined by rescanning, with the reference axis. If any suchadjustment is required, a conventional display indicates the degree ofadjustment and thus the degree of inaccuracy which must be corrected byrecalibration, repair or adjustment as required.

SYSTEMS RELATING TO LONGITUDINAL DIMENSION OF LOG

Certain systems are incorporated in the charger 10 which relate to thelongitudinal positioning and control of each log rather than to itsoptimum peeling axis. These systems primarily enhance the productionrate of the charger and lathe.

When each log 14 is deposited from the conveyer 16 onto the conveyor 18,a pair of arms 22 actuated by a pair of fluid ram assemblies, havingassociated position sensors, servo valves and controllers (not shown),grasp the ends of the log to sense its length while simultaneouslyshifting it longitudinally such that one of its ends (i.e. itscontrolled end) is flush with an imaginary line extending parallel tothe edge of the conveyer 18.

The length sensing information derived from the positions sensors ofarms 22 is utilized by the charger in a number of different ways. First,logs too short or too long for veneer peeling are immediately identifiedand can be discarded from the conveyer 18 onto the ejection conveyer 42either automatically or by operator manual override so that no time islost scanning these logs and transferring them to the lathe. Second, thelength information is compared with the subsequent positions of thelog-engaging devices 26, rotary scanner spindles 28 and transfer arms 32as they extend toward each other to engage the log to determine theexact time when full engagement of the log is achieved by each set oflog manipulators. Such full engagement can be sensed as the time whenthe space between opposing manipulators, as indicated by their positionsensors, equals the known length of the log. At this point, themanipulators are automatically actuated to begin to move the logaccording to their predetermined functions without the need for anydelay to provide a margin of safety to ensure full engagement. Also, bycomparing the known log length with the subsequent engagement positionsof the respective sets of log manipulators, it can be determined whetherany set of manipulators has, in fact, engaged the log. For example ifthe signals from position sensors 60, 80 or 106, at the time that theirrespective log manipulators are supposed to be engaging a log of knownlength as sensed by the arms 22, indicate that their respectivemanipulators have closed to positions separated by less than the knownlength of the log, such discrepancy indicates that the log has not beengrasped for some reason. Accordingly such discrepancy is indicatedautomatically by any suitable means to bring the problem to theattention of the operator, preferably by interrupting extension andactuation of the set of manipulators automatically in response to suchdiscrepancy to permit the operator to manually control the appropriatelog manipulators to correct the problem.

As mentioned above, besides length-sensing, the arms 22 have the furtherfunction of positioning one end (the controlled end) of each log along apredetermined imaginary line parallel to the edge of the conveyer 18.Subsequent log-engaging devices 26, 28 and 32 which subsequently engagethe same end of the log likewise are controlled, by their respectivefluid ram assemblies, position sensors, valves and controllers, so as tolimit their extension to positions for maintaining such end of the logflush with such imaginary line. This ensures that the controlled end ofthe log, when ultimately mounted in peeling position in the lathe 12,retains its alignment with such imaginary line. The object of suchlongitudinal log position control is to ensure that the controlled endof each log longitudinally overlaps outwardly, and thus engages, one ofthe scoring knives 123 (FIG. 1) conventionally positioned adjacent eachend of the lathe's peeling knife 36, such knives serving to form thelongitudinal edges of the veneer sheets peeled from the log. Thisfeature, in cooperation with the detection by arms 22 of logs ofinsufficient length and the resultant ejection of such logs from thecharger, ensures that both ends of each log extend outwardly beyond thescoring knives when the log is in peeling position. Without suchlongitudinal log position control the operator would have to checkvisually the positions of the two scoring knives relative to each log,and then longitudinally adjust the position of the log in the lathe ifthe ends of the log did not overlap both scoring knives, prior tobeginning the peeling operation.

In summary, the foregoing interaction between the length-sensing andlongitudinal positioning arms 22 and the subsequent log manipulators 26,28 and 32 serves to eliminate numerous time delays which would otherwisebe repeated on a regular basis as logs are processed.

LOG MANIPULATOR POSITIONING SYSTEMS

FIG. 9 depicts schematically a typical double-acting hydraulic ramassembly and its associated position sensor, servo valve and controlleremployed to control virtually all of the log manipulators of the charger10. In particular, the diagram of FIG. 9 is typical of the systemutilized for the following ram assemblies and position sensors (exceptthat items 2, 3 and 6 below actually employ solenoid-operated valvesrather than servo valves):

1. ram assembly 54 and position sensor 56 of log-engaging device 26;

2. ram assembly 58 and position sensor 60 of log-engaging device 26;

3. ram assembly 68 and position sensor 80 for extending and retractingeach rotary scanner spindle 28;

4. ram assemblies 88 and position sensor 90 for horizontally adjustingthe position of each rotary scanner spindle 28;

5. ram assembly 94 and position sensor 96 for vertically adjusting theposition of each rotary scanner spindle 28;

6. ram assemblies 104 and position sensors 106 for controlling theclamping and unclamping of transfer arms 32; and

7. ram assemblies 116 and position sensors 118 for controlling the logtransfer movement of transfer arms 32.

In general, the reciprocating motion of each ram assembly, and theresultant movement of each log manipulator to which the ram assembly isconnected, is controlled by a servo valve which admits hydraulic fluidselectively to either side of the ram assembly's piston depending uponthe position of the spool of the servo valve. The position of the valvespool depends upon signals received from a controller in response to thecontroller's comparison of two input signals. The first input signalcomes from the position sensor connected to the particular logmanipulator being controlled. The position sensor, which operates on aconventional principle to be described hereafter, is a precisionposition measuring device which continually follows the movement of thelog manipulator and transmits a signal which changes incrementally withchanges in position so that the controller can sense the preciserelative position of the log manipulator. The controller's second inputsignal is from a system for determining the desired position of the logmanipulator. For example, in the case of ram assembly 54, the secondinput signal is from the preliminary scanner 24. Alternatively, in thecase of ram assemblies 88 and 94, the second input signal is from finalscanner 30. In the case of ram assemblies 116, the second input signalwould be from peeling knife position sensor 122. For ram assemblies 58,68 and 104 on the controlled end of the log, the second input signalwould represent the predetermined position of the controlled end.

When the controller, in comparing the actual position signal (input 1)with the desired position signal (input 2), determines that extension ofthe ram assembly is required to move the log manipulator to the desiredposition, it moves the servo valve spool toward the right as shown inFIG. 9. Conversely, when it senses that retraction of the ram assemblyis required to move the log manipulator to the desired position, itmoves the servo valve spool toward the left. When its comparison of thetwo inputs indicates that the log manipulator is in the desiredposition, it centers the servo valve spool. The controller makes suchcomparison repeatedly in rapid succession to ensure that the particularlog manipulator is moved to, and then maintained in, its desiredposition.

The controller's second input signal can, in some cases, also constitutea reference signal. For example, in the case of ram assemblies 58, 68and 104 on the uncontrolled end of the log, the second input signalwould represent log length-sensing information from the position sensorsof arms 22 which the controller compares with the signal from therespective position sensor 60, 80 or 106 to determine whether completeengagement or nonengagement, as the case may be, has occurred.

It is important to note that the fluid ram assemblies which act as thepower actuators for the various log manipulators do not also serve asposition sensors for their respective log manipulators, as is the commonpractice with comparable positioning systems. Instead, each positionsensor is a separate unit connected to the log manipulator separatelyand independently of the connection of the ram assembly. Thus the wearwhich occurs at the connection between each ram assembly and itsrespective log manipulator due to the transfer of substantial forcetherethrough does not affect the separate connection of the respectiveposition sensor to the same log manipulator, and therefore the positionsensors retain their high degree of accuracy. Since positioning accuracydepends principally upon the accuracy of the position sensors ratherthan the ram assemblies, the accuracy of the positioning system remainshigh. Moreover, the maintained accuracy of the position sensors enablesthem to detect excessive wear in their associated ram assemblyconnections as indicated by excessive overshooting of a desiredposition, and the resultant necessity for excessive position correction.Such overshooting is recorded on a printout or display therebyidentifying the location of the wear.

FIGS. 10 and 11 depict two different types of conventional positionsensors utilized in the present invention. FIG. 10 shows a linearposition-sensing device having an oil-filled cylinder 124 within which apiston 126 and piston rod 128 reciprocate in response to the movement ofthe object whose position is to be sensed, to which the piston rod 128is connected. The piston 126 has a permanent magnet therein andsurrounds an elongated nonmagnetic beam 132. The principle of operationof the position sensor of FIG. 10 is fully disclosed in U.S. Pat. No.3,898,555, which is incorporated herein by reference. Position sensors56, 90, 96 and 118 are constructed in accordance with FIG. 10.

The position sensor of FIG. 11 comprises a reciprocating rod 134connected to the manipulator whose position is to be sensed. Movement ofthe rod 134 in response to movement of the manipulator causes movementof a chain 136 to which the rod 134 is attached. Movement of the chain136 in turn rotates a rotary encoder connected to either of sprockets138 or 140 as the case may be. The rotary encoder generates signals in aknown manner which vary with the degree of rotation of the encoder asdetermined by the position of the manipulator. Position sensors 60, 80,and 106 are constructed in accordance with FIG. 11.

PRESSURE-BIASED BEARING SYSTEM

A further important feature which reduces the effect of wear upon theaccuracy of the charger is the provision of fluid pressure-biasedbearing pads for those log manipulators which precisely adjust theposition of the log for proper alignment of its optimum peeling axis.These include those bearing pads, such as 78 and 86, associated witheach rotary scanner spindle 28 abutting the various slidable elementsthereof by which the spindle is extended and retracted and adjustedhorizontally and vertically. Also included are the bearing pads whichguide the vertical slides 48 and horizontal slides 52 of the respectivelog-engaging devices 26.

For purposes of illustration, pressure-biased bearing pads 142 whichguide horizontal slides 52 of each log-engaging device 26 will beexplained in detail as typical of all of the pressure-biased bearingpads. Each such elongate bearing pad is movably mounted within a slideguide frame 144 so as to be movable toward the slide in a directiontransverse to the sliding direction thereof. Behind each bearing pad 142is a row of pistons 146, each slidably mounted in a bore 148 and sealedby a U-cup 150. Behind each piston 146 is a fluid cavity formed betweenthe piston and a respective threaded plug 152. Each bore of a respectiverow of pistons 146 communicates with a source of pressurized hydraulicfluid 154 through a respective conduit 156. The pressure of the fluid inconduit 156 exerts a predetermined fluid pressure on the respectivepistons 146, which in turn is transferred to the respective bearing pad142 and slide 52. The predetermined fluid pressure is determined by thepressure of the fluid source 154 exerted through a conduit 158 andpressure reducing valve 159 upon the side of a respective piston 160having the lesser area of its two sides. Thus the pressure actuallyexerted through conduit 156 on the pistons 146 is somewhat less than thepressure at the source 154 in accordance with the setting of thepressure reducing valve 159 and the ratio of the areas of the two sidesof the piston 160.

As natural wear to the respective bearing pad 142 occurs, it nonethelesscontinues to exert the same pressure upon the slide 52 and no loosenessin the engagement of the slide with the slide guide frame 144 is therebypermitted to occur. It will be noted that, in order to prevent suchlooseness, it is not necessary to provide pressure-biased bearing padsin opposing relationship to each other; rather a fixed bearing pad suchas 162 can oppose a pressure-biased bearing pad such as 142. As wear ofthe respective bearing pad 142 occurs, both the rear side of the bearingpad and the pistons 146 move toward the slide 52 thereby permitting morepressurized fluid to enter the cavities behind the pistons 146. Suchfluid is drawn from the large area side of the piston 160 causing somesmall retraction of the piston 160 and its associated piston rod 164.

No significant retraction of the piston and rod will occur, however,unless there is leakage of fluid past the pistons 146. In such event therelative extension of the rod 164 serves as an indicator for sensingflow of pressurized fluid into the cavities and thus leakage. Before thepiston 160 becomes fully retracted due to loss of fluid due to leakage,the retraction of the piston rod 164 closes an electrical switch 166which actuates an appropriate alarm or printout 167 to signal theimpending loss of fluid pressure on the respective bearing pad 142. Suchsignal enables the operator to open a valve 168 so as to allow fluid toflow from the fluid source 154 to the large area side of the piston 160.Because of the area difference on the two sides of the piston 160, suchopening of the valve 168 causes the piston 160 and piston rod 164 toextend so as to replenish the fluid on the large area side of the piston160. Full extension of the piston 160 reopens switch 166. Opening ofvalve 168 could alternatively be automatic in response to switch 166 ifdesired. In this manner leakage can easily be detected from the relativeextension of the piston rod 164 before the reduction of fluid pressureon the pad 142, thereby permitting repair of the system before any harmis done.

Preferably the pistons 146 of each pressure-biased bearing pad 142 areconnected by their own separate conduit, such as conduits 156 and 170,to their own separate piston 160, switch 166 and valve 168 so that thepressure exerted on each pad can be set and any leakage thereofmonitored and pinpointed separately.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

What is claimed is:
 1. A charger for a veneer lathe comprising:(a) rotary means for engaging opposing ends of an elongate log and rotating said log longitudinally about an axis of rotation; (b) scanning means for sensing the shape of said log while it is rotated by said rotary means for determining the location of the longitudinal axis of the log for optimum production of veneer; (c) adjusting means responsive to said scanning means for moving said rotary means at opposite ends of said log along axes transverse to said axis of rotation of said rotary means so as to align said longitudinal axis of said log with a reference axis, said adjusting means including means for moving said rotary means along said axes while said rotary means are rotating said log; and (d) transfer means for transferring said log from alignment of said longitudinal axis with said reference axis to alignment of said longitudinal axis with the rotational axis of said veneer lathe.
 2. A method for charging a veneer lathe comprising:(a) engaging opposing ends of an elongate log and rotating said log longitudinally about an axis of rotation; (b) sensing the shape of said log while it is being rotated and determining the location of the longitudinal axis of the log for optimum production of veneer; (c) simultaneously with the rotation of said log, moving the opposite ends of said log along axes transverse to said axis of rotation and thereby aligning said longitudinal axis of said log with a reference axis; and (d) transferring said log from alignment of said longitudinal axis with said reference axis to alignment of said longitudinal axis with the rotational axis of said veneer lathe. 